Ligand Orientation-Induced Lattice Robustness for Highly Efficient and Stable Tin-Based Perovskite Solar Cells

Low-toxicity tin-based perovskites have exhibited huge potential for photovoltaics applications. However, the facile oxidation of Sn2+ to Sn4+ induces ubiquitous Sn vacancies and p-type doping in perovskite films. In addition, the fast crystallization easily leads to poor film morphology and high defect concentration. In this work, we developed a film-formation strategy via the fluoro-aniline isomers medium and achieved the simultaneous restriction of Sn2+ oxidation and regulation of crystallization. The ortho-fluorine ligand, which exhibits unidirectional and bent geometry at the surface, could contribute to the lattice robustness with better restriction of Sn vacancy formation, compared with the bidirectional and vertical ligands. The resulting perovskite solar cell (PSC) device modified by 2-F-PEA shows a considerable PCE of 10.17% (certified 8.58%), with an efficiency attenuation of less than 15% under 1600 h of light aging testing. Our findings could provide a new avenue for the enhancement of both efficiency and stability of tin-based PSCs.